The invention relates to acousto-optic beam deflectors, and more particularly to an acousto-optic beam deflector characterized by deflecting both polarization components of an optical beam with equal efficiency.
Conventional acousto-optic beam deflectors utilize a longitudinal acoustic wave transducer to produce a traveling longitudinal acoustic wave in a piece of isotropic stress optic material, such as glass. The traveling acoustic wave modulates the index of refraction of the glass through the stress optic effect. The incident light beam is then diffracted by the traveling phase grating produced by the traveling acoustic wave. For sound propagating parallel to the x axis, light which is propagating parallel to the z axis and is polarized parallel to the y axis will be more strongly diffracted than light polarized parallel to the x axis.
It is possible to produce an acousto-optic beam deflector which affects both polarizations equally, by inducing an acoustic shear wave into the stress optic medium instead of a longitudinal acoustic wave. However, acoustic shear waves are less efficiently produced and suffer greater attenuation then longitudinal acoustic waves once in the stress optic medium.
The foregoing and related prior art are discussed in detail in Chapter 12 of Introduction to Optical Electronics, by Amnon Yariv, 1976, published by Holt, Reinhard & Winston.